A cross-point type memory device including a variable resistance element in a memory cell has been recognized as a large capacity, nonvolatile memory device. In particular, a Conductive Bridging Random Access Memory (CBRAM), which is a cross-point type memory device, can be formed with a general semiconductor process and material. The CBRAM is attracting attention as a nonvolatile memory device of the next generation because writing current and erasing current are very small and data holding performance is high.
Since the CBRAM has a simple structure, it may be easily formed in a stereoscopic structure. When manufacturing a stereoscopic CBRAM, word lines and bit lines are alternately arranged in the stacking (vertical) direction and each memory cell is arranged between each word line and vertically adjacent bit line. For example, the stacking order of each layer within a memory cell arranged between a word line and a bit line is opposite to the stacking order of each layer within a memory cell arranged between the word line and a bit line arranged under the word line.
With such a stacking order, even when the material of each layer forming each memory cell is common in all the memory cells, the order of arranging each layer is opposite and the film formation condition is not the same. With the advance in miniaturization, each layer forming a memory cell has to be thin, and when the stacking order changes, there is a fear that the quality of film cannot be consistently maintained in each layer.